With the growing number of sequenced genomes, there has been a greater opportunity for proteome research (see Non-Patent Document 1). After the success of the DNA array chips which brought a revolution in genome researches, the “protein array chips” that are capable of high-throughput analysis of the expression and interaction of proteins are greatly sought after (see Non-Patent Document 2). Specifically, studies focusing on the functionality of membrane proteins are important since they are vital in regulating the transport of various molecules in and out of cells.
However, handling membrane proteins such as ion channels, pumps, receptors, and transporters has been challenging as they only function when embedded in a lipid layer, i.e., a fundamental structure of all bio-membranes (see Non-Patent Document 3). As a result, the primary targets of most protein chips have been mostly water-soluble proteins.
Patch clamping (see Non-Patent Document 4) and artificial lipid bilayer (see Non-Patent Document 5) experiments have been two major established methods in the fundamental studies of membrane proteins. However, both methods require the experienced skills to perform and have not realized good reproducibility due to a lack of high-throughput operations. Recently, several research groups have tried to overcome these problems by working on generating planar bilayers in microfluidic devices (see Non-Patent Documents 6-8). Integrated microfluidic systems offer a vast array with advantages including portability, decreased analysis time, a smaller amount of required reagents, and parallel automation with high reproducibility. Although realizing these benefits leads to the high-throughput and quantitative measurements for analyzing membrane transport, such simple techniques or devices have not existed yet.    Non-Patent Document 1: V. Santoni, M. Molley, T. Rabillound, “Membrane proteins and proteomics: Un amour impossible?”, Electrophoresis, 21, 1054-1070, 2000    Non-Patent Document 2: H. Zhu, M. Bilgin, R. Bangham, David Hall, Antonio Casamayor, P. Bertone, N. Lan, R. Jansen, S. Bidlingmaier, T. Houfek, T. Mitchell, P. Miller, R. A. Dean, M. Gerstein, and M. Snyder, “Global Analysis of Protein Activities using Proteome Chips”, Science., Vol. 293, 2101-2105, 2001    Non-Patent Document 3: M. Bloom, E. Evans, O. G. Mouritsen, “Physical Properties of the Fluid Lipid-Bilayer Component of Cell Membranes: a Perspective”, Q. Rev. Biophys., Aug.; 24(3), 293-397, 1991    Non-Patent Document 4: B. Alberts et al., “Molecular Biology of the Cell; 4th Ed.,”, Garland Science, 2002    Non-Patent Document 5: T. Ide, and T. Yanagida, “An Artificial Lipid Bilayer Formed on an Agarose Coated Glass for Simultaneous Electrical and Optical Measurement of Single Ion Channels”, Biochem. Biophys. Res. Comm., 265, pp. 595-599, 1999    Non-Patent Document 6: R. Hemmier, G. Bose, E. Wagner, and R. Peters, “Nanopore Unitary Permeability Measured by Electrochemical and Optical Single Transporter Recording”, Biophys., Vol. 88, 4000-4007, 2005    Non-Patent Document 7: N. Malmstadt, M. A. Nash, R. F. Purnell, and J. J. Schmidt, “Automated Formation of Lipid-Bilayer Membranes in a Microfluidic Device”, Nano Lett., Vol. 6, No. 9, 1961-1965, 2006    Non-Patent Document 8: M. Mayer, J. K. Kriebel, M. T. Tosteson, and G. M. Whitesides “Microfabricated Teflon Membranes for Low-Noise Recordings of Ion Channels in Planar Lipid Bilayers”, BioPhys., Vol. 85, 2684-2695, 2003